JPS61158803A - Apparatus for synthesis of compound semiconductor polycrystal - Google Patents

Abstract

PURPOSE:To provide an apparatus synthesizing polycrystalline product in a short time, in high recovery based on the raw material, by placing an independent sublimation heater at the circumference of a raw material container fixed to the upper shaft in a liquid-encapsulated pulling up apparatus, and attaching a porous cap to the lower end of a connection tube. CONSTITUTION:A group III or group II solid or liquid raw material and a liquid encapsulation material (solid) are charged in the crucible 7. A solid raw material 2 consisting of group V or group VI element is charged in the container 1, and the container 1 is sealed and fixed to the upper shaft 11. The connection tube 3 is not inserted into the crucible 7. A pressure vessel is closed, and the space in the vessel is pressurized sufficiently by introducing an inert gas such as N2, Ar, etc. The raw material and the liquid encapsulation material are melted with the molten liquid heater 9 to obtain molten liquids 5 and 6. The lower end of the tube 3 is dipped into the liquid 5. The raw material 2 is heated and gasified with the sublimation heater 10 to increase the pressure in the vessel sufficiently, when the gas is released to the liquid 5 in the form of fine bubbles through the porous cap 4 attached to the lower end 19 of the tube 3. The effective surface area of the raw material 2 is increased by this process to facilitate the reaction and the escape of unreacted raw material from the liquid 5 can be prevented almost completely.

Description

[Detailed description of the invention] ('7) Techniques Branch field The present invention relates to an apparatus for synthesizing compound semiconductor polycrystals.

The compound semiconductor referred to here refers to a ■-■ group compound semiconductor or an I-■ group compound semiconductor.

m-v group semiconductors are InP, GaAs, GaP
, InAs 11nSb s, etc.

...-■ group semiconductors are CdSe, CdTe, Zn
SSHgSe.

There are combinations such as...

These semiconductor single crystals are used for light emitting devices, light receiving devices, FETs, etc.
It is useful as a substrate for other sensors.

In order to make a single crystal, polycrystalline materials of these compound semiconductors are required as raw materials. To make polycrystals, two types of raw materials must be synthesized.

b) Subordinate techniques A polycrystalline synthesis method for InP will be explained.

The melting point of InP is 1062° C., but the vapor pressure of P at this temperature is 27.5 atm, which is extremely high. Generally, the high vapor pressure at the melting point of a group IV compound of a group V element makes it difficult to synthesize stoichiometric polycrystals.

Synthesis of InP is usually carried out by the gradient freeze method. In and P are sealed in a quartz ampoule at positions separated from each other. 11 with two independent heaters separated in the axial direction
Place the ampoule horizontally into the heated device.

Adjust the heater power to create a horizontal temperature distribution.

, the synthesis region of InP should be near its melting point, but the region where P is present should be at a lower temperature to prevent the P vapor pressure from increasing. P vapor moves through the ampoule and reacts with In to form InP. By gradually shifting the relative positions of the ampoule and the heater, all the materials were converted to InP.
I'm going to change K.

However, the gradient freezing method
In the part where P became present, there was a tendency for P to become insufficient and In to become excessive. Therefore, the final synthesized near-end tube cannot be used as an InP polycrystal. When using it as a material for growing single crystals, it was necessary to melt only the final synthesis end beforehand and remove this part.

Therefore, instead of the gradient freeze method, a method was proposed in which polycrystals were synthesized using a bipolar capsule pulling device.

The liquid capsule crystal pulling device is a crystal growing device using a pulling method. A single crystal is grown by placing a raw material melt in a crucible, soaking a seed crystal, and pulling it up while rotating.The melt is covered with a liquid capsule layer and strong pressure is applied with nitrogen gas, argon gas, etc. It prevents group elements from escaping.

For this reason, the liquid capsule method, or simply the LEG method (Liqui
id Encapsulated Czochruls
ki).

LEC equipment is originally intended for producing single crystals, but since it is equipped with a high-pressure K[temperature] container, a heater, an upper shaft, a lower shaft that can be rotated up and down, a susceptor, etc., it is suitable for the synthesis of polycrystalline materials. It was thought that it could also be suitably used.

Jaxml of'Crystal Growth
59 (198,2) P, 665-6681A M
ETHOD FORTHIi: 'lN-5ITU'
5YNTHESIS AND GROW THOF IN
DIUM PH0SPHIDE IN A CZOCH
In RALSKIPULLERJ, J, P, and FMGFS conducted I
We report on the synthesis of nP.

Figure 2 shows the LEC device used by Farges.

A graphite susceptor 32 supported by a lower shaft 31 is contained in a pressure vessel 30, and a quartz crucible 3 is surrounded by the graphite susceptor 32.
3. Graphite heater 34, Graphite a-shielding cylinder 35
etc. will be provided.

Peephole 36 and gas inlet 3 on the side of pressure capacity 2g30
7 etc. An upper shaft 38 is provided above the pressure container 30 so as to be rotatable up and down.

When used as a single crystal pulling device, a seed crystal is attached to the lower end of the upper shaft 38.

However, since this device is used for synthesis, red phosphorus P is held by the upper shaft 38. A graphite holder 39 is fixed to the lower end of the upper shaft 38, and within the holder 39 is a quartz ampoule 40.

A thermocouple 41 is provided to measure the temperature of the amplifier/I/40. A vertical communication tube 42 is inserted into the center of the amplifier/I/40, and its upper end opens near the upper wall of the ampoule.

The crucible 33 contains an In melt 43 and a B2O3 τ-body capsule layer 44 for encapsulating it.

Ampoule 40 contains red phosphorus 45.

The temperature at the bottom of the crucible 33 is measured using a thermocouple 46.

The lower end of the communicating tube 42 is dipped into the In melt 43.

Both the crucible 33 and the ampoule 40 are lowered from top to bottom while keeping the distances between the crucible 33, the ampoule 40, and the upper and lower shafts of the picks constant. Since the heat from the heater 34 is strongly applied, the temperature of both the crucible and the ampoule rises as the crucible descends.

In this example, the distance between the bottom of the crucible and the ampoule is 150ff.
I keep it at ff. The temperature of the ampoule can be changed from 400<0>C to 700<0>C by means of a descending operation.

The pressure vessel 30 is filled with argon gas of 6Q atm.

As red phosphorus is gradually heated, it sublimates and becomes a gas.

The vaporized phosphorus is transferred from the upper end opening of the communication pipe 42 to fJ ii
It descends in the Q tube 42, enters the In water liquid 43, and becomes bubbles. The phosphorus in the bubbles and the indium in the melt combine to form an InP melt. If all In becomes a compound,
The synthesis is finished. When the melt temperature is lowered, inside the crucible,
InP polycrystals can be obtained.

However, this method has the following drawbacks.

The phosphorus gas enters the melt in the form of bubbles. , since the bubbles are light, the melt, g! l Ascent through the capsule layer. Although the reaction occurs while the melt passes through iT1, the reaction time is not sufficient.

Therefore, there are many phosphorus bubbles that reach the liquid force/L'lfi. This passes through the γ-covered capsule layer as it is. No matter how high the argon gas pressure is, it cannot prevent air bubbles from escaping the liquid capsule layer.

The one-liquid capsule has the effect of suppressing the release of P due to decomposition of the InP compound due to high heat.

The evaporation percentage of P is diffused into the pressure container. In addition, phosphorus adheres to the inner wall surface of the pressure container.

The present inventor has checked that the recovery rate for the raw materials (In and P) for InP polycrystals by the Farges method is about 80%. Too much waste.

1.5 moles of P are required per 1 mole of In. If this is not done, unreacted In will remain in the crucible.

That is, in this example, about 1/3 of P is wasted without participating in synthesis.

Another drawback is that the synthesis time is too long. This is because the reaction area is small.

(1) Purpose (1) To provide a synthesis device with a high recovery rate of synthesized polycrystalline material based on raw material elements.

(2) It is an object of the present invention to provide a polycrystal synthesis apparatus that requires a short synthesis time.

2) Configuration The device of the present invention uses an LEC device, and the crucible has ■, ■
Put the group melt, and put the group ■ and ■ elements in the storage container fixed in the upper case. An independent sublimation heater is provided around the storage container. It is the same as Farges in that the storage container and crucible are connected by a straight pipe, but in order to reduce the straight lines of air bubbles, a porous cap is provided at the lower end of the communicating pipe.

The compound semiconductor polycrystal manufacturing apparatus of the present invention will be explained with reference to FIG.

Since the LEG device is used, there is a pressure-resistant container around it, but it is not shown here.

The upper @ 11 is provided in a pressure-resistant container so that it can rotate and move up and down.

When pulling a single crystal, a seed crystal is attached to the lower end of the upper shaft 11. However, since an LEC device is used for synthesis here, a storage container 1 containing a raw material solid 2 of group Y (P, As1Sb) elements or group II elements (S, 5eSTe) is fixed to the upper shaft 11. It is. The material of storage container 1 is
PBNSBN, quartz, or BN-coated carbon may be used.

The contained raw material solid 2 is heated by a heater 10 provided around the storage container 1, and sublimated to become a gas.

The sublimation heater 10 is not present in a normal crystal pulling apparatus, and in the present invention, this heater is newly added. Farges's experiment did not use such a heater, but instead controlled the temperature with a single heater for the melt, which limited the distance between the storage container and the crucible, making adjustment difficult.However, the present invention uses a sublimation heater. 10, the adjustment becomes easy.

The lower shaft 12 is also rotatable and can be moved up and down. At the upper end of the lower shaft 12,
A susceptor 8 is fixed, and a crucible 7 is inserted into the susceptor 8.

The material of the susceptor 8 is carbon or the like. Crucible 7 is P
It is made of BN, quartz, etc. A melt heater 9 is provided around the susceptor 8 and crucible 7. This is a carbon resistance heater.

A shielding tube for preventing heat from escaping to the outside is provided further outside the heater 9, but is not shown here.

The crucible γ accommodates a raw material @liquid 5 and a liquid capsule layer 6 covering the upper part thereof. Raw material melt 1fUI11 pieces (Ga, In) or group II (Cd, Zn, T
e) Of elements! It's Toru 1 night.

The storage container 1 and the raw material melt 5 in the lower crucible 7 are connected by a straight communication pipe 3.

The material of the communication tube 3 is PBN, BN, quartz, BN-coated carbon, or the like. The upper wall 13 of the storage container 1 is the upper shaft 1
1, but there is a through hole 1γ in the center of the lower wall 14.
The communication tubes 3 are inserted upward through the through hole 17 and are fixed to each other around this hole.

The upper opening 18 of the tube 3 is located close to the upper wall 13. The raw material solid 2 is filled to a level l below the upper opening 18. This is because solid raw materials must not fall into the crucible.

The lower end 19 of the communication tube 3 is closed with a porous cap 4. The material of the porous cap 4 is quartz, PBN, B.
N, carbon, AIM, Si3N4, etc.

Porous means that there are countless narrow, winding passageways inside.

It has a structure similar to the inside of a sponge or activated carbon. Porous materials and media are often used to increase the efficiency of chemical reactions because they have an extremely large surface area, through which liquids or gases can pass, and the reaction area is large.

However, the intention here is not to directly increase the speed of chemical reactions through the use of porous materials. Therefore, the large effective area inside the porous material is not directly utilized. In this respect, it differs from the usual use of porous materials.

Here, when the gas of the group (1) or group (2) elements exits the melt from the communicating tube, it becomes bubbles, and porosity is used to reduce the average diameter of the bubbles.

Since the existence of bubbles itself is non-equilibrium, the diameter of the bubbles cannot be determined accurately. However, we can discuss the bubble diameter in terms of probability.

If the porous cap 4 is not provided, gas will come out all at once from the wide opening at the bottom, and this will easily cause a bunch of large bubbles to disappear.

Since the gas exits through the porous gap 4 instead of through the openings, it becomes bubbles with a small average diameter.

Below, we will discuss probabilistic considerations.

During a melting night, there is usually convection, but there are also irregular flows. However, under static conditions without such disturbances, let us consider what volume V of bubbles would be generated from a diameter pore. For simplicity, this pore is assumed to be an upward pore.

When bubbles are formed, they have upward buoyancy. @ Let ρ be the difference in density between the liquid and the bubbles. The buoyant force is ρvg. g is the gravitational acceleration. The force that binds the bubble to the opening is surface tension, but since the diameter of the pore is D, the surface tension per unit length is T, and the V at the moment the bubble leaves the pore is ρVg = πD T
(Satisfies formula 11. At this time, the bubble has an amorphous shape, but it becomes spherical as soon as it leaves the pore. If the radius of this bubble method is a, then it becomes. In other words, the radius of the bubble method is 1/3 of the pore diameter
Proportional to the power.

This is the case for upward facing pores. For downward pores,
It will be larger than this. However, in reality there are disturbances,
Even air bubbles coming out of the downward facing pores are pulled away from the bottom surface of the pores.

The separation force due to disturbance is proportional to the cross-sectional area. Then (1
), instead of kA = πD T (8
The expression + holds true. k is a constant, A is IN? It is the area. In this case, the radius a of the bubble is proportional to the 1/2 power of the aperture.

The second idea was to estimate the diameter of a bubble from the balance of the bubble when it is floating. It is assumed that the radius a of the bubble is proportional to 1/2 to 1/3 of the diameter of the opening.

Next, consider what size bubbles are stable in the melt. This is the pressure P in the liquid. What happens to the diameter of the bubble depending on the difference between the pressure inside the bubble and the pressure P (of course P>Po)? That's what it means. The difference between the pressure inside and outside the bubble is written as ΔP. If the number of bubbles increases by dV, the surface tension energy increases accordingly.

This means that the surface area of the bubble is S and its increment is ds, and TdS
It is expressed as Also, the work done on the melt is PdV
It is. Therefore, ΔPdV = 'rcts (
5) Then, 2-cho P-Po = ΔP = -(61. This means that the smaller the diameter of the bubble, the greater the pressure inside the bubble. Po is the pressure of the melt and It is almost constant and is determined by the pressure of external N2 gas and argon gas.

Equation (6) means that in order to generate small bubbles, the pressure P inside the bubbles must be significantly large.

Po is the sum of the pressure of the inert gas and the pressure corresponding to the depth of the liquid capsule to the lower opening of the melt.

Since the latter pressure is small, the inert gas pressure P. That's what it means.

Initially, the pressure inside the storage container 1 is also equal to Po.

When the raw material solid 2 is heated and sublimated, the pressure is slightly higher than this, and gas exits from the lower end of the communication pipe.

If there is no cap (like the Farges device)
Since the gas immediately escapes into the melt, the internal pressure of the storage container 1 does not rise. The toe D (P-Po) is extremely small.

Then, from equation (6), it can be seen that the diameter of a stable bubble is extremely large.

If there is a porous cap as in the present invention, vaporized moths will not easily pass through this camp. Therefore,
The internal pressure of the storage container 1 can rise to a sufficiently high level. Of course, this internal pressure is not equal to the pressure when passing through the cap. However, if the internal pressure is high, the pressure passing through the cap may also be high. That is, (P-Po) is large.

Therefore, bubbles with a small diameter can be stably produced.

(3) Action Place the Group I or Group II solid or liquid raw material and a liquid capsule (solid) into a crucible. A solid raw material of a group (■) or group (■) element is placed in a storage container 1.

The container 1 is sealed and fixed to the upper shaft 11.

The communication tube 3 is not inserted into the crucible. Close the pressure container and introduce an inert gas such as nitrogen gas or argon gas to create a sufficiently high pressure.

The melt heating heater 9 is energized to melt the raw material, and also melt the liquid and body capsule. Both become molten liquid. The lower end of the communicating tube 3 is inserted into the melt. The sublimation heater 10 is energized to heat the raw material solid 2. The raw material that has become a gas increases the internal pressure of the storage container 1. When sufficient pressure is reached, the communication pipe 3
Small gas bubbles form from the porous cap 4 at the lower end 19 of the g! Go out into 5.

During this time, the bubbles and the components of the melt undergo a chemical change and become a compound melt.

When all the raw material solids 2 are gone, it means that everything has passed through the melt 5, and this is the end of the synthesis. The upper shaft 11 is pulled up, and the communication tube 3 is pulled up from the melt 5. A liquid capsule layer overlies the melt. After this, the heater power is reduced and the temperature is lowered.

Polycrystals are produced within the crucible.

Φ) Effect (11 Ratio of group ■ and group ■ from the porous cap [Gas with high closing pressure is blown into the melt little by little, so the diameter of the bubbles becomes extremely fine. Since the effective surface area is large, the melt It easily reacts with the liquid.Therefore, almost no unreacted substances escape from the melt.

Therefore, the recovery rate of the synthetic compound relative to the raw material is extremely high. It is 90% or more.

(2) There is a porous cap at the bottom end of the communication pipe, so
Even if there is an imbalance between the internal and external pressures, the melt will not flow back to the upper storage container.

G) Example InP polycrystals were synthesized from In and P using an apparatus as shown in FIG. Charger is in the crucible In (red phosphorus) t5oog
B203 (liquid power press I) 120g In the storage container P 480g. The inside of the LEC device is filled with N2 gas, and 5Q a
It was designated as tm.

The temperature inside the crucible is raised by the melt heating heater 9.

The In FfA solution was kept at 1065°C. The storage container 1 containing the raw material red phosphorus is lowered so that the lower end of the communicating tube is located in the melt.

The outer layer heater 10 heats phosphorus to sublimate it.

The temperature of this container was kept at about 350℃ for a while, and
'& Gradually raise the temperature to 550℃.

The amount of InP polycrystals synthesized as a result was 1905 g. The recovery rate is 98.7%.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a compound semiconductor polycrystal synthesis apparatus of the present invention. Figure 2 shows the L used by J. P. Farges in the synthesis of InP.
A cross-sectional view of the EG device. 1 ... Storage container 2 ... Raw material solid 3 ... Communication pipe 4 ... Porous cap 5 ... Raw material melt 6 ... ...Liquid capsule layer γ... Crucible 8 ... Susceptor 9 ... Melt heating heater 10 ... Sublimation heater 11 ...・Top shaft 12...Bottom shaft 13...Soil Wall 14...Bottom wall 17...Through hole 18...Top opening Inventor Satoshi Kotani Ryo Hisashi Hirokawa Patent applicant Sumitomo W1 Industries Co., Ltd. No. 1
Figure 2 (Procedure amendment system) % formula % 1. Indication of the case Japanese Patent Application No. 59-281270 2, Title of the invention Compound semiconductor polycrystalline synthesis device 3, Person making the amendment Relationship with the case Patent applicant Location 5-15 Kitahama, Higashi-ku, Osaka Name (213) Sumitomo Electric Industries Co., Ltd. Representative President Tetsube Kawa 4, Agent Kumo 537 Address 3-15-16 Nakamichi, Higashinari-ku, Osaka Liquid Capsule Puller A method was proposed to synthesize polycrystals using the above device. The liquid capsule crystal pulling device is a crystal growing device using a pulling method. A single crystal is grown by placing a raw material melt in a crucible, soaking a seed crystal, and pulling it up while rotating.The melt is covered with a liquid capsule layer and strong pressure is applied with nitrogen gas, argon gas, etc. This prevents group V elements from escaping. For this reason, the liquid capsule method, or simply the LEC method (Liqui
It is called id 膓呵Betsudo mlC 迒く１ ici).

Claims (1)

[Claims] A lower shaft 12, a susceptor 8 supported by the lower shaft 12, a crucible 7 provided in the susceptor 8 and containing a raw material melt of group III or group II elements and a liquid capsule layer 6, and a crucible 7 of the crucible 7. A melt heating heater 9 provided around the melt heating heater 9, an upper shaft 11, a storage container 1 for containing the raw material solid 2 of group V or VI element supported by the heater 9, and a storage container 1 provided around the storage container 1. A sublimation heater 10 that heats the raw material solid 2, a communication pipe 3 communicating with the storage container 1 such that the upper opening 18 is located at the top of the storage container 1, and an opening at the lower end 19 of the communication pipe 3 are provided. An apparatus for synthesizing compound semiconductor polycrystals, characterized in that it comprises a porous cap 4 with a polycrystalline structure.